Fungicidal compositions based on copper salts are well known to kill a wide variety of fungus on contact. However, these preparations act only on the external surfaces of plants and are not absorbed by plant tissues. Thus, these compositions only control the external fungi manifestation of infected vegetation while leaving unaffected the internal manifestation. That is, vegetation infected by fungus suffer internal damage, for example, the plugging of the food conducting tissues at the union between the stock and scion which quickly kills the vegetation. Hence, it is desired that a fungicide not only kill fungi on the surface of the vegetation but also enter the plant system and be active therein.
The term "vegetation" herein is intended to mean any plant, cane, vine, shrub, bush, tree or any vegetation in general.
Attempts have been made to find a satisfactory method for effectively combating fungi such as coffee tree rust (Hemileia vastatrix Berk.). However, known treatments have not achieved a satisfactory degree of success beyond a partial control of the external manisfestation of the fungi.
Various iodophor compositions are well known in the art to be suitable as bactericides and fungicides. More specifically, U.S. Pat. No. 4,271,149 teaches germicidal iodine compositions comprising an aqueous solution of iodine, iodide ion, iodate ion and an organic substance which slowly reacts with iodine, for example, a surface active agent such as ethoxylates of alkyl phenols. In such compositions, the free iodine level is maintained for extended periods of time by the presence of both an iodate ion and a buffer to control the pH within the range of 5-7. Such compositions are disadvantageous in that they require both the addition of an iodate ion and a buffer for maintenance of the pH range.
U.S. Pat. No. 4,288,428 teaches an iodophorous disinfecting composition comprising an iodophor in the form of an alkyl phenoxy poly(ethyleneoxy)-ethanol-iodine complex. This iodophor complex contains 5-10% by weight urea and an acid in an amount sufficient to maintain a pH between 1-5. This composition is disadvantageous in that it requires the use of both urea and an acid to control the pH as well as a solvent.
U.S. Pat. No. 4,113,857 discloses a method for producing an organic iodophor germicidal composition comprising reacting an organic iodophor forming compound, for example, nonyl phenoxy poly(ethyleneoxy)-ethanol with an iodine adding agent, for example, potassium iodide, and hydriodic acid in the presence of an oxidizing stabilizer such as potasium iodate. This iodophor preparation is disadvantageous since it requires the use of hydriodic and an iodate.
U.S. Pat. No. 344,056 discloses a disinfectant consisting of a mixture of ammonium chloride, potassium iodide dissolved in water and iodine. However, this composition is disadvantageous since it is not very stable.